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Amount of selected biologically active compounds in Stevia rebaudiana
Porubčanová, Vladimíra ; Jurečková, Zuzana (referee) ; Vespalcová, Milena (advisor)
This bachelor thesis deals with plant, called stevia rebaudiana and analysis of phenolic compounds in the extracts from it. The theoretical part describes its botanical characteristics, chemical constitution and effect on humans health. This thesis is interested in sweetener, produced from stevia, comercionally used as E 960: steviol-glykosides, too. There is listed register of companies producing this sweetener and food products, where stevia is used in. The experimental part of thesis is focused to analysis of total phenolic content in stevia extracts, because leaves of stevia are primary used for sweetening of tea. The main aim of the thesis was find out, how is total phenolic content changed during extraction of leaves in time, in water with different temperature and in different samples.
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Determination of steviol glycosides in beverages
Porubčanová, Vladimíra ; Diviš, Pavel (referee) ; Vespalcová, Milena (advisor)
This diploma thesis deals with sweet substances from Stevia rebaudiana and with their determination in beverages. The ambition was to adjust the separation method for major steviol glycosides (stevioside and rebaudioside A) by HPLC so as to be fast and effective enough, too. In experimental part was successfully developed the separatin method, so it is possible to determine the steviol glycosides and conservation substances, specifically benzoic and sorbic acid (eventually their sodium or potassium salts). At first, for analysis was used monolithic column, on which stevioside and rebaudioside A weren´t separated. Other analyses were performed on column Ascentis express C18 (150 x 4.6; 2.7 µm). The most suitable separation method was performed by mobile phase made up with 29:71 v/v mixture of acetonitrile and acetate buffer (with pH 4.2). The flow rate was 0.28 ml/min and the column temperature was kept constant at 50 °C. The analysis of steviol glycosides and conservation substances with these condition was verified on the samples of real beverages.
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Determination of steviol glycosides in beverages
Porubčanová, Vladimíra ; Diviš, Pavel (referee) ; Vespalcová, Milena (advisor)
This diploma thesis deals with sweet substances from Stevia rebaudiana and with their determination in beverages. The ambition was to adjust the separation method for major steviol glycosides (stevioside and rebaudioside A) by HPLC so as to be fast and effective enough, too. In experimental part was successfully developed the separatin method, so it is possible to determine the steviol glycosides and conservation substances, specifically benzoic and sorbic acid (eventually their sodium or potassium salts). At first, for analysis was used monolithic column, on which stevioside and rebaudioside A weren´t separated. Other analyses were performed on column Ascentis express C18 (150 x 4.6; 2.7 µm). The most suitable separation method was performed by mobile phase made up with 29:71 v/v mixture of acetonitrile and acetate buffer (with pH 4.2). The flow rate was 0.28 ml/min and the column temperature was kept constant at 50 °C. The analysis of steviol glycosides and conservation substances with these condition was verified on the samples of real beverages.
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Amount of selected biologically active compounds in Stevia rebaudiana
Porubčanová, Vladimíra ; Jurečková, Zuzana (referee) ; Vespalcová, Milena (advisor)
This bachelor thesis deals with plant, called stevia rebaudiana and analysis of phenolic compounds in the extracts from it. The theoretical part describes its botanical characteristics, chemical constitution and effect on humans health. This thesis is interested in sweetener, produced from stevia, comercionally used as E 960: steviol-glykosides, too. There is listed register of companies producing this sweetener and food products, where stevia is used in. The experimental part of thesis is focused to analysis of total phenolic content in stevia extracts, because leaves of stevia are primary used for sweetening of tea. The main aim of the thesis was find out, how is total phenolic content changed during extraction of leaves in time, in water with different temperature and in different samples.
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